Apparatus and method for multiple channel high throughput purification

ABSTRACT

A multiple channel high throughput purification system for purifying a plurality of samples, preferably four or more samples from a chemical library. The high throughput purification uses chromatography, and more preferably, super critical fluid chromatography. Four parallel channels are provided in this system and coupled to a common analyzer and computer. The four channels direct the selected sample flow through a separator, such as an SFC column, a detector, such as a UV detector, to detect peaks within the sample flow, and a micro sample valve that splits a sampling of the flow to an analyzer, such as a mass spectrometer. The system also utilizes unique back pressure regulator assemblies and pressure relief assemblies to maintain a selected pressure within the purification channel. While the sample flow continues, the mass spectrometer simultaneously analyzes the sampling to determine if a target compound is within the sample portion. A fraction collection valve directs sample portions to one of two fraction collectors such as a microtiter plate. The purified target compounds are collected in one microtiter plate and the other non-desirable peaks are collected in a second microtiter plate in corresponding wells. In the supercritical fluid chromatography purification system, an expansion chamber is provided to condense the vaporous sample flow before the purified compounds are added to the particular well of the microtiter plate. A fraction collection assembly is used that automates the use of disposable expansion chambers for depositing the samples in the microtiter plates.

TECHNICAL FIELD

The present invention is directed to apparatus and methods of samplepurification, and more particularly, to apparatus and methods of highthroughput purification of samples from a chemical library.

BACKGROUND OF THE INVENTION

The relationship between structure and functions of molecules is afundamental issue in the study of biological and other chemistry-basedsystems. Structure-function relationships are important inunderstanding, for example, the function of enzymes, cellularcommunication, cellular control and feedback mechanisms. Certainmacromolecules are known to interact and bind to other molecules havinga specific 3-dimensional spatial and electronic distribution. Anymacromolecule having such specificity can be considered a receptor,whether the macromolecule is an enzyme, a protein, a glycoprotein, andantibody, or an oglionucleotide sequence of DNA, RNA, or the like. Thevarious molecules which bind to receptors are known as ligands.

A common way to generate ligands is to synthesize molecules in astepwise fashion in a liquid phase or on solid phase resins. Since theintroduction of liquid phase and solid phase synthesis methods forpeptides, oglionucleotides, and small organic molecules, new methods ofemploying liquid or solid phase strategies have been developed that arecapable of generating thousands, and in some cases even millions ofindividual compounds using automated or manual techniques. A collectionof compounds is generally referred to as a chemical library. In thepharmaceutical industry, chemical libraries of compounds are typicallyformatted into 96-well microtiter plates. This 96-well formatting hasessentially become a standard and it allows for convenient methods forscreening these compounds to identify novel ligands for biologicalreceptors.

Recently developed synthesis techniques are capable of generating largechemical libraries in a relatively short period of time as compared toprevious synthesis techniques. As an example, automated synthesistechniques for sample generation allows for the generation of up to4,000 compounds per week. The samples, which contain the compounds,however, typically include 20%-60% impurities in addition to the desiredcompound. When samples having these impurities are screened againstselected targets, such as a novel ligand or biological receptors, theimpurities can produce erroneous screening results. As a result, samplesthat receive a positive result from initial screening must be furtheranalyzed and screened to verify the accuracy of the initial screeningresult. This verification process requires that additional samples beavailable. The verification process also increases the cost and timerequired to accurately verify that the targeted compound has beenlocated.

Samples can be purified in an effort to achieve an 85% purity or better.Screening of the purified samples provides more accurate and meaningfulbiological results. Conventional purification techniques, however, arevery slow and expensive. As an example, conventional purificationtechniques using high-pressure liquid chromatography (HPLC) takeapproximately 30 minutes to purify each sample. Therefore, purificationof the 4,000 samples generated in one week would take at least 2000hours (i.e. 83.3 days or 2.77 months).

Conventional purification techniques, such as HPLC, also require largevolumes of solvents and result in large volumes of waste solvent.Disposal of the solvents, particularly halogenated solvents, must becarefully controlled for legal and environmental reasons, so thedisposal process can be laborious and very costly. Disposal ofnon-halogenated solvents is less rigorous. Accordingly, when halogenatedand non-halogenated solvents are used, the waste solvents are separated.The separation process of large volumes of solvents, however, can be adifficult process to perform efficiently and inexpensively. Accordingly,purification of large chemical libraries can be economicallyprohibitive. Therefore, there is a need for a faster and more economicalmanner of purifying samples of large chemical libraries.

Supercritical fluid chromatography (SFC) provides faster purificationtechniques than HPLC. SFC utilizes a multiphase flow stream thatincludes a gas, such as carbon dioxide, in a supercritical state, acarrier solvent and a selected sample. The flow stream passes through achromatography column, and is then analyzed in an effort to locatetarget compounds. SFC is beneficial because the solvent and sample arecarried by the gas and the amount of solvent needed during apurification run is substantially less than the volume used in HPLC.Also, the amount of waste solvent at the end of a run is substantiallyless, so less waste solvent needs to be handled. SFC, however, requirespressure and temperature regulation that is difficult to controlaccurately and reliably long term.

There are many different configurations of the purification instruments.They typically share commonality in the concept wherein that samples aredelivered to a chromatography instrument where compounds are separatedin time, and a fraction collector collects the target compound. In orderfor these instruments to maintain the high throughput process, theinstruments must be able to handle large sample numbers, as well aslarge samples in terms of mass weight and solvent volume. Traditionwould specify the use of a semiprep or prep scale chromatography systemfor a typical milligram synthesis. While this is achievable, it has alow feasibility in a high throughput environment because several issuesbecome apparent in such practice: large solvent usage, generation oflarge amounts of solvent waste, expensive large-bore columns, andrelatively large collection volumes of target compounds. If the properflow rate or column size is not used, sufficient chromatographic puritywill not be achieved.

Further drawbacks experienced with high throughput purificationtechniques include durability of components to accommodate the highpressures, high volumes, or high flow rates of samples through thepurification system. The purification system requires extreme accuracyand very high tolerances to avoid cross-contamination and to ensurepurified compounds. The system components, thus, must be sufficientlydurable to accept the aggressive environment while still providing theaccurate results required. If the components are not sufficientlydurable and they break or require repair too quickly, the purificationsystem must be taken out of service to replace or repair the components.

A further drawback experienced in conventional purification processes oflarge chemical libraries includes sample management during thepurification process. As an example, the chemical libraries aretypically maintained in sets of 96-well microtiter plates, wherein eachwell includes a separate sample. Each sample is carefully tracked by its“well address” within the microtiter plate. When a sample or portion ofa sample is removed for purification from a selected well of amicrotiter plate, the purified sample is typically collected in aseparate container, processed, and eventually returned to a receivingwell in a similar microtiter plate. That receiving well preferably has acorresponding well address in the microtiter plate so as to maintain theaccuracy of the library records regarding sample location in therespective microtiter plate.

Conventional purification processes typically require the reformattingof a purified sample because the large collected volumes of fluid (e.gthe solvent that contains the purified sample) is greater than thevolume of a receiving well in a conventional microtiter plate. The largecollected volumes must be reduced to a volume that fits into themicrotiter plate's well. The reduced volume of fluid containing thepurified sample is also tracked and deposited into the appropriate wellof the receiving microtiter plate that correctly maps to the welllocation from which the sample was taken at the start of thepurification run. Such reformatting of purified samples into thereceiving microtiter plate increases the time requirements and cost ofthe purification processes. Therefore, there is a need for apurification process that allows for quick and economical purificationof samples that result in purified samples being collected directly tomicrotiter plates mapped directly to the original plate.

SUMMARY OF THE INVENTION

The present invention is directed to apparatus and methods of multiplechannel high throughput purification of samples from a chemical librarythat overcome drawbacks experienced in the prior art. In an illustratedembodiment of the present invention, the method of multiple channel highthroughput purification simultaneously purifies a plurality of samples,such as four samples, from a chemical library.

The method of the illustrative embodiment includes simultaneouslypurifying by supercritical fluid chromatography (SFC) all four samplesin four channels of a purification system. The method includes passing afirst sample along a SFC flow path of the first channel, separating thefirst sample into sample portions, spacing the sample portions apartfrom each other along at least a portion of the first fluid path. Thepressure of the supercritical fluid in the flow stream is regulated witha backpressure regulator and a pressure relief valve. The method alsoincludes moving the separated sample portions along the fluid path, anddetecting at least one sample portion flowing along the fluid path. Themethod further includes diverting a sampling away from the sampleportion, directing the sampling to an analyzer while the remainder ofthe sample portion continues along the fluid path, analyzing thesampling with the analyzer, and determining if the one sample portionhas selected sample characteristics. The method also includes collectingthe one sample portion in a first receptacle, such as a well of a firstmicrotiter plate, only if the sample portion has the selected samplecharacteristics. If the sample portion does not have the selected samplecharacteristics, the sample portion is collected in a second receptacle,such as a corresponding well in a second microtiter plate.

The multiple channel high throughput purification method of thisillustrated embodiment further includes purifying a second sample alonga second channel substantially simultaneously with the purification ofthe first sample. Purifying the second sample includes passing thesecond sample along a second flow path of the second channel, separatingthe second sample into sample portions, and spacing the sample portionsapart from each other along at least a portion of the second fluid path.The method also includes moving the separated sample portions along thesecond fluid path, and detecting at least one of the sample portionsflowing along the second fluid path. The method includes regulating thesecond sample's pressure along the flow path. The method furtherincludes taking a sampling from the one sample portion and directing thesampling to the same analyzer used for the first channel. The remainderof the sample portion continues to flow along the second fluid path.

The method also includes analyzing the second sampling with theanalyzer, wherein the first and second samplings are analyzed separatelyin accordance with a selected analysis priority protocol. The analysisof the second sampling determines if the sample portion has selectedsample characteristics. The method further includes collecting thesample portion in a separate receptacle, such as a separate well in thefirst microtiter plate identified above, only if the sample portion hasthe second selected sample characteristics. If the sample portion doesnot have the selected sample characteristics, the sample portion iscollected in another receptacle, such as a separate well in the secondmicrotiter plate identified above.

In one embodiment of the invention, the method of high throughputpurification includes purifying third and fourth samples alongcorresponding third and fourth channels in a manner similar to thepurification discussed above regarding the first and second samples. Inthis embodiment, the same analyzer is used to analyze samplings from allfour samples. The samplings are all analyzed separately and inaccordance with the selected analysis priority protocol.

The invention is also directed to a multiple channel high throughputpurification system for substantially simultaneously purifying aplurality of samples from a chemical library. In one illustratedembodiment, the system includes a controller and a sample analyzercoupled to the controller, wherein the analyzer is configured todetermine whether the samplings have selected sample characteristics.First, second, third, and fourth purification channels are coupled tothe sample analyzer. The first purification channel includes aseparation device positioned to receive a sample flow and to separate afirst sample into sample portions so the sample portions are spacedapart from each other in the sample flow. A detector is positioned toreceive the sample flow from the separation device and to detect atleast one sample portion within the first sample. An adjustablebackpressure regulator receives the flow stream from the detector andcontrols the pressure of the flow stream within the first channel.

A microsampling device is positioned to receive the sample flow from thebackpressure regulator and is movable between open and closed positionswhile allowing a substantially continuous flow stream to pass throughthe device. In the closed position, the microsampling device blocks theflow stream from passing to the analyzer and allows the flow streamcontinues to flow through the device. In the closed position, themicrosampling device also allows a substantially continuous flow ofcarrier fluid to pass therethrough to the analyzer. In the openposition, the microsampling device directs a sampling of at least theone sample portion to the analyzer for analysis, while a remainder ofthe one sample portion in the sample flow moves substantiallyuninterrupted through the microsampling device.

A pressure relief valve receives the remainder sample flow from themicrosampling device and maintains a selected pressure in the sampleflow downstream of the microsampling device. A flow directing valve isin fluid communication with the first flow path and is positioned toreceive the sample flow downstream of the pressure relief valves. Theflow directing valve is moveable to a first position to direct the onesample portion in one direction if the analyzer has determined that theone sample portion has the selected sample characteristics. The flowdirecting valve is movable to a second position to direct the one sampleportion in another direction if the analyzer has determined that the onesample portion does not have the selected sample characteristics. Afirst receptacle, such as a well of a microtiter plate, is positioned toreceive the one sample portion from the flow directing device when theflow directing device is in the first position because the sampleportion has the selected characteristics. A second receptacle, such as awell in a second microtiter plate, is positioned to receive the onesample position when the flow directing device is in the second positionbecause the sample portion does not have the selected characteristics.

The second purification channel of the purification system includes aseparation device positioned to receive a second sample flow and toseparate a second sample into sample portions. A separate detector iscoupled to the separation device and is positioned to receive the secondsample from the separation device. The detector is configured to detectat least one of the sample portions within the sample flow. Amicrosampling device is positioned to receive the sample flow from thedetector and is movable between open and closed positions. When themicrosampling device is in the closed position, the microsampling deviceallows the second sample flow to pass therethrough while being blockedfrom passing to the analyzer. In the open position, the microsamplingdevice directs a sampling of the one sample portion to the analyzer foranalysis, while the remainder of the sample portion continues along thesecond flow path substantially uninterrupted. A back pressure regulatorand a pressure relief valve receive the second sample flow upstream anddownstream, respectively, of the microsampling device to selectivelycontrol the pressure of the second sample flow along the secondpurification channel. A flow directing valve is in fluid communicationwith the second flow path and is positioned to receive the sample flowtherethrough. The flow directing valve is moveable to a first positionto direct the one sample portion in one direction if the analyzer hasdetermined the sample portion has the selected sample characteristic.The flow directing valve is moveable to a second position to direct theone sample portion in another direction if the analyzer has determinedthat the sample portion does not have the selected samplecharacteristics.

A receptacle, such as a separate well in the first microtiter plate, ispositioned to receive the sample portion from the flow directing devicewhen the flow directing device is in the first position because thesample portion has the selected characteristics. Another receptacle,such as a separate well in the second microtiter plate, is positioned toreceive the sample portion when the flow directing device is in thesecond position because the sample portion does not have the selectedcharacteristics.

In one embodiment of the invention, the purification system includesthird and fourth purification channels that purify third and fourthsamples substantially simultaneous with the purification of the firstand second samples. Each of the third and fourth purification channelsare coupled to the same analyzer and direct the sample portions toreceptacles, such as wells in the first and second microtiter plates,discussed above.

An aspect of the invention provides a microsample or flow splitter valvefor use in the high throughput purification system for purifying aselected sample from a chemical library. The purification system has asample flow path, a carrier fluid flow path, and a sample analyzer influid communication with the sample and carrier flow paths. Themicrosample valve includes a valve body having an interior chambertherein, and sample flow inlet and outlet ports in fluid communicationwith the sample flow path and with the interior chamber. The valve bodyhas a carrier fluid flow port in fluid communication with the carrierfluid flow path, and an outflow port channel in fluid communication withthe analyzer. A stem is slidably disposed in the interior chamber and ismoveable between first and second positions within the chamber. The stemhas a fluid bypass channel that communicates with the sample inlet portand the outflow port when in the first position to allow a selectedportion of the sample to flow to the analyzer. The stem blocks thecarrier flow port when in the first position to prevent fluid from thecarrier fluid flow path from moving into the outflow port.

The fluid bypass channel in the stem communicates with the carrier flowport and with the outflow port when in the second position to allowselected carrier fluid to flow through the valve body to the analyzer.The stem blocks the sample flow inlet port from communicating with theoutflow port when in the second position to prevent the sample flow fromflowing to the outflow channel.

An aspect of the invention also includes an automated fractioncollection assembly that retains the microtiter plates in a fixedposition and dispenses the sample portions into the selected wells inthe microtiter plates. The fraction collection assembly includes adispensing needle through which the sample portion is dispensed intodisposable expansion chambers and then into the microtiter plate. Thedispensing needle is mounted on a dispensing head adapted to extend intoa disposable expansion chamber into which the sample portion iscondensed and then dispensed into the microtiter plate.

The dispensing head is movable from a pick-up position, where theexpansion chambers are picked up, to a collection position over themicrotiter plates, where the sample portions are dispensed into theselected well of the microtiter plate. The dispensing head is alsomovable from the dispensing position to a chamber drop-off position,where the expansion chambers are released into a waste receptacle, sothe dispensing needles are exposed. The dispensing head is furthermovable to a wash position at a wash station on the fraction collectionassembly, where the dispensing needles are washed to avoidcross-contamination between samples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of one portion of a multiple channel highthroughput purification system in accordance with an embodiment of thepresent invention.

FIG. 2 is a schematic view of another portion of the multiple channelhigh throughput purification system of FIG. 1.

FIGS. 3A and 3B are schematic views of the multiple channel highthroughput purification system of FIGS. 1 and 2, wherein the system hasfour channels.

FIG. 4 shows a side elevation view of a two-piece column of thepurification system of FIG. 3 in accordance with one embodiment of theinvention.

FIG. 5 shows a cross-sectional view of the two-piece column takensubstantially along line 5—5 of FIG. 4.

FIG. 6 shows a side elevation view of a one-piece column in accordancewith an alternate embodiment of the invention.

FIG. 7 shows a cross-sectional view of the one-piece column takensubstantially along line 7—7 of FIG. 6.

FIGS. 8A-C show three chromatographic runs showing the improvement overprior art.

FIG. 9 is an enlarged exploded isometric view of a back pressureregulator assembly from the purification system of FIG. 3.

FIG. 10 is an enlarged exploded isometric view of a back pressureregulator module from the assembly of FIG. 9.

FIG. 11 is an enlarged isometric view of a regulator/motor assembly ofthe back pressure regulator module of FIG. 10.

FIG. 12 is an enlarged cross-sectional view of the regulator assemblytaken substantially along line 12—12 of FIG. 11.

FIG. 13 is an enlarged isometric view of a microsample valve assemblyfrom the purification system of FIG. 3.

FIG. 14A is an isometric view of a microsample valve from the assemblyof FIG. 13.

FIG. 14B is an enlarged, exploded isometric view of a microsample valvefrom the assembly of FIG. 13.

FIG. 15 is a plan view of a valve body of the microsample valve of FIG.14.

FIG. 16 is an enlarged cross-sectional view taken substantially alongline 16—16 of FIG. 14, the microsample valve being shown in anon-sampling position.

FIG. 17 is an enlarged cross-sectional view taken substantially alongline 17—17 of FIG. 14, the microsample valve being shown in a samplingposition.

FIG. 18 is an enlarged cross-sectional view of a dispensing head and anexpansion chamber from the purification system of FIG. 3, the dispensinghead being shown in a dispensing position.

FIG. 19 is an isometric view of an automated fraction collectionassembly of the purification system of FIG. 3, the assembly shown in achamber pickup position.

FIG. 20 is an isometric view of the fraction collection assembly of FIG.19 shown in a collection position.

FIG. 21 is an isometric view of the fraction collection assembly of FIG.19 shown in a chamber drop-off position.

FIG. 22 is an isometric view of the fraction collection assembly of FIG.19 shown in a rinse position.

DETAILED DESCRIPTION OF THE INVENTION

The structure and function of exemplary embodiments of the presentinvention can best be understood by reference to the drawings. The samereference numbers may appear in multiple figures. The reference numbersrefer to the same or corresponding structure in those figures.

A multiple channel high throughput purification system 10 in accordancewith an illustrated embodiment is shown in FIGS. 1-3, and components ofwhich are shown in FIGS. 4-22. The illustrated purification system 10 isconfigured to simultaneously purify four samples 12 from a chemicallibrary, wherein each sample is purified along a respective purificationchannel 14 in the system. Purification in the illustrated embodiment isachieved by chromatography, and more particularly by super criticalfluid chromatography (SFC), discussed in greater detail below.

Each channel 14 receives a selected sample from a supplying microtiterplate 20. Each channel 14 is coupled to a common analyzer, such as amass spectrometer 16 that analyzes selected portions of the samples inaccordance with a predetermined analysis priority protocol. In oneembodiment, the analyzer includes a plurality of compound identificationdevices. In the illustrated embodiment, each supplying microtiter plate20 includes a bar code or other selected symbology or tracking mechanismthat provides information specific to that supplying microtiter plate.The purification system 10 includes a bar code reader 15 or the likethat identifies the specific supplying microtiter plates 20 used foreach purification run.

The components of each channel 14, including the mass spectrometer 16and the bar code reader 15, are coupled to a computer controller 18 thatmonitors and controls operation of the components during a purificationrun. The mass spectrometer 16 is also connected to a computer 17 thatcan provide a user with additional control or monitoring capabilitiesduring a purification run.

After each sample 12 is analyzed by the mass spectrometer 16, asubstantially purified sample portion is distributed directly into acorresponding well of a receiving microtiter plate 22 (FIG. 2) oranother selected sample collector. The other portions of the sampledetected by the detector, know as crudes, are distributed directly intoa corresponding well in a second microtiter plate 24, also illustratedin FIG. 2. Accordingly, the four samples 12 are drawn from the supplyingmicrotiter plate 20, purified, and each sample is deposited directlyinto a corresponding well location in two receiving microtiter plates 22and 24 , one containing the purified target compound and the othercontaining the crudes. In one embodiment, the four samples are drawnfrom the supplying microtiter plate sequentially by the same drawingneedle assembly. In an alternate embodiment, the four samples are drawnsubstantially simultaneously by a drawing assembly having four drawingneedles.

The receiving microtiter plates 22 and 24 have bar codes or the like onthem, and a bar code reader 25 (FIG. 2) is provided adjacent to thereceiving microtiter plates. The second bar code reader 25 is alsocoupled to the computer controller 18 (FIG. 1) to identify and track thesamples deposited into the selected wells of each microtiter plate. Thepurified target compounds in the microtiter plates 22 and 24 can then bescreened in a selected manner in an effort to locate a specific targetcompound.

The microtiter plates 22 are securely retained in an automated fractioncollection assembly 23 coupled to the computer controller 18 (FIG. 1).The fraction collection assembly 23 directs selected sample portions ofeither purified target components or purified crudes to selected wellsof the microtiter plates 22 or 24. The fraction collection assembly 23is automated and configured to pick up, clean, disposable or reusableexpansion chambers in which vaporous sample portions are condensed andthen delivered to the microtiter plates 22 or 24. The fractioncollection assembly 23 includes a wash station in which sampledispensing needles are washed after a sample portion is delivered to therespective microtiter plate and before the next set of clean expansionchambers are picked up for delivery of the next sample portions.

In the purification process of the illustrated embodiment, selectedsupplying microtiter plates 20 are identified by the bar code reader 15and positioned on an autosampler 21 (FIG. 1). In one embodiment, theautosampler 21 is a Gilson 215 autosampler, manufactured by Gilson, Inc.of Middleton, Wis. As best seen in the schematic diagram of FIG. 3, eachsample is drawn by the autosampler 21 from a selected well of asupplying microtitor plate 20 and is fed into a sample flow path 30 of arespective one of the four channels 14. The four samples 12 aresubstantially simultaneously introduced into the respective purificationchannels 14. Although the illustrated embodiment substantiallysimultaneously purifies four samples 12, other numbers of samples can besimultaneously purified with a system in accordance with the presentinvention.

As best seen in FIG. 3, the sample 12 is combined with carbon dioxidefrom a CO₂ source 29 and a modifier solvent from a solvent source 33 toform a carrier flow that flows through the respective channel 14 at aselected flow rate. The carbon dioxide flows through a heat exchanger 36is chilled with a recalculating cooling bath 35 and is pumped via a CO₂pump 37 to a mixer 39. The flow of CO₂ is also passed through a pulsedamper to minimize any pulsation caused by the pump 37. The modifiersolvent flows through a solvent pump 41 into the mixer 39 where thesolvent is mixed with the carbon dioxide. The carbon dioxide and solventmixture then flows to a sample injection valve 43, where the sample 12is received from the autosampler 21 is combined with the carrier flow toform the sample flow 31.

The sample flow 31 is passed through a heat exchanger 45 at which timethe fluid becomes supercritical, and then a separation media, such as anSFC column 32, that separates the sample components within the sampleflow 31. Accordingly, each sample component is spaced apart from theother components as the sample flow exits the SFC column 32 and movesthrough the purification channel 14.

In one embodiment of the invention, the column 32 is a two-piece column,as illustrated in FIGS. 4 and 5, for use in supercritical fluidchromatography. As best seen in FIG. 4, the components of the column 32include an upper dilution body 400 that defines that a dilution chamber408 therein. The top portion of the dilution body 400 is connected to aninlet tube 410 through which the sample flow 31 passes and moves intothe column 32. The upper dilution body 400 is connected to a loadingbody 402 and securely retained in place by a top end cap 401. Thedilution chamber body 400 is compressed downwardly by the top end cap401 that screws externally onto the threads of the loading body 402. Inan alternate embodiment for use in liquid chromatography, the dilutionchamber is not needed, so the column 32 does not include the dilutionbody attached to the loading body.

The dilution chamber body 400, the top end cap 401, and the loading body402 of the illustrated embodiment are made from an inert material, suchas stainless steel. In alternate embodiments, other inert materials canbe used for construction of the column's components. A separation body403 at its upper end is attached to the lower portion of the loadingbody 402. The lower end of the separation body 403 is securely connectedto a bottom end cap 404 that connects to an outlet tube 412, throughwhich the separated sample flow 31 exits the column 32.

As best seen in a cross-sectional view of FIG. 5, the sample flow 31enters the column 32 at a top-threaded port 505 to which an inlet tube410 is sealed by an external ferrule that seats onto the top ferrulesealing point 506 in the threaded port. The sample flow is directedradially from the inlet tube 410 into the upper dilution chamber 408 bymeans of an inverted top funnel portion 507. The top funnel portion 507is substantially conical in geometry and it defines the top of thedilution chamber 408. The main body of the dilution chamber 408 issubstantially cylindrical, although it can be constructed with othergeometric shapes in alternate embodiments. The bottom of the dilutionchamber 408 has an inverted bottom funnel portion 509 that flaresradially outwardly from the dilution chamber's main body. Accordingly,the bottom funnel portion 509 flares to a lower opening having a greaterdiameter than the dilution chamber's main body. The lower opening of thebottom funnel portion 509 is positioned over a top frit 510 locatedbelow the dilution chamber 408.

The dilution chamber's entire volume is void of stationary phasematerial. Dilution of the sample in the sample flow takes place in thedilution chamber 408 as the sample flow moves downwardly through themain body to the bottom funnel portion 509, where the sample flow passesthrough the top frit 510. The top frit 510 distributes the sample over acolumn bed 512 in a loading region 520 directly below the top frit 510.Sealing of the dilution chamber 408 is achieved at the top frit 510where the dilution chamber body 400 fits internally into the loadingbody 402.

The loading body 402 has a loading region 520 below the top frit 510 anda transition region 522 below the loading region. The loading andtransition regions 520 and 522 in the loading body 402 are filled with astationary phase material, such as cyano, that defines a column bed 512in the column 32. In alternate embodiments, other stationary phasematerials can be used to form the column bed 512. The loading region 520has an inner diameter approximately two or more times greater than theinner diameter of the separation region 524, and a length ofapproximately one-half or less than the length of the separation region.In the loading region 520, the sample flow traverses downwardly throughthe column bed 512 into the transition region 522, which has a conicalshape as defined by the loading body 402. The transition region 522directs the sample flow into the separation region 524 of the column bed512.

The top of the separation body 403 is threadably attached to the bottomof the loading body 402 by a threaded connection and is sealed by anadjoining frit 511 sandwiched therebetween. The separation body 403 ofthe illustrated embodiment is made of stainless steel and is shaped sothe interior chamber containing the separation region 524 of the columnbed 512 has a tapered cylindrical geometry with a wider upper end and anarrower lower end. The interior chamber of separation region 524 of thecolumn bed 512 is filled with the stationary phase material. The sampleflow travels downwardly through the column bed 512 in the separationregion 524 past a bottom frit 513 and onto a bottom fluid funnel 514formed in the bottom end cap 404. The bottom of the separation region524 is sealed by the bottom end cap 404 screwed externally onto theseparation body 403. The bottom frit 513 is sandwiched between thebottom end cap 404 and the separation body 403. The bottom fluid funnel514 is conical and directs the fluid into a bottom threaded port 516formed in the bottom end cap 404 to which the outlet tube 412 can bescrewed. The outlet tube 412, when screwed into the outlet port 516, issealed against the bottom end cap 404 at a bottom ferrule sealing point515 by use of an external ferrule.

In an alternate embodiment illustrated in FIG. 6, the column 32 is a“one-piece” column. In view of the similarities between the twoembodiments, components that are the same between the two embodimentsare identified in the figures by the same reference numbers for purposesof clarity. The one-piece column is substantially the same as thetwo-piece column discussed above, with the exception that the loadingbody 602 and the separation body 603 are integrally formed from a singlestainless steel unit to define a One-Piece Loading and Separation(OPLAS) body 617. Accordingly, the upper frit 511 used in the two-piececolumn is not needed and thus omitted.

As best seen in the cross-sectional view of FIG. 7, the dilution chamberbody 400 fits internally into the OPLAS body 617 and is secured by thetop end cap 401 that screws externally onto the OPLAS body. The lowerend of the OPLAS body 617 screws internally into the bottom end cap 404.Accordingly, the loading region 520 formed in the OPLAS body 517 has adiameter approximately two or more times greater than the inner diameterof the separation region 524, and a length of approximately one-half orless than the length of the separation region.

FIGS. 8A-C show graphical results from three chromotographic runsshowing improvement over the prior art provided by the column 32 inaccordance with the present invention. All three chromotographic runswere injected with the same mass loading of a three-compound mixture andrun under the same chromotographic conditions. Run 200 (FIG. 8A) showsthe separation results using a single prior art column injected with asmall volume solvent mixture. Run 201 (FIG. 8B) shows the separationresults using the same prior art single column as in run 200, whereinthe prior art column was injected with a large volume solvent mixture.Run 202 (FIG. 8C) shows the separation results using a two-part column32 in accordance with an embodiment of the present invention asdiscussed above. Run 202 was injected with the same large volume solventmixture as run 201.

The first portions of the column 32 (e.g., the loading and transitionportions) have a larger inner diameter than the column's second portion(the separation region) and a shorter length than the column's secondportion. Accordingly, the column 32 in accordance with the presentinvention can handle large volume solvent mixtures with multiplecompounds and provide highly accurate separation and detection of thedifferent compounds, such as by use of a mass spectrometer or the like.This accuracy in conjunction with corresponding speed for handling largevolume solvent mixtures with multiple compounds provides a faster andmore efficient processing capability.

Referring again to FIG. 3, the sample flow 31 exits the SFC column 32,flows through another heat exchanger 47, and flows to a detector 34. Thedetector 34 is adapted to detect the different components or peaks inthe sample flow 31 that have been separated from each other by the SFCcolumn 32. In the illustrated embodiment, the detectors 34 areultraviolet light (UV) detectors. While UV detectors are used in theillustrated embodiment, other detectors can be used, such as infrared(IR) detectors or any other suitable detector capable of identifying apeak within the sample flow 31.

Each detector 34 is coupled to the common computer controller 18. Whenthe detector 34 identifies a peak, the detector provides a signal to thecomputer controller 18 indicating the peak. Because the sample flow rateis known in each channel 14, the computer controller 18 can calculatethe location of each peak within each channel 14 as the sample flow 31moves through the channel. As an example, when two peaks are detected inthe same sample flow 31, the computer controller 18 calculates andmonitors where those peaks are within the channel 14. The computercontroller 18 also calculates where the peaks are relative to each otherduring the entire purification process.

As the sample flow 31 moves through the purification channel, it is in avaporous state. After the sample flow 31 exits the detector 34,additional solvent, referred to as makeup solvent 49, is added to thesample flow as needed to increase the volume of liquid in the sampleflow to facilitate transport of the sample to the fraction collectorassembly (discussed below). The makeup solvent 49 is pumped from asolvent container by solvent pumps 51 into the respective purificationchannel 14. The solvent container and the solvent pumps 51 are eachcoupled to the computer controller 18 so the computer controller canmonitor the solvent volumes used and can control the solvent pumps asnecessary for the selected purification run. The computer controller 18also monitors the amount of makeup solvent 49 needed within thepurification channel during a run, so it can detect if a potentialproblem arises, and can provide an alarm or other warning to an operatorof the system.

After any of the makeup solvent 49 is added to the sample flow 31, thesample flow passes through a back pressure regulator module 53 in a backpressure regulator assembly 55. The back pressure regulator module 53detects and controls the back pressure within the channel 14 to maintainthe desired pressure within the channel.

As best seen in FIG. 9, the back pressure regulator assembly 55 includesa housing 900 that removably retains four back pressure regulatormodules 53, one for each purification channel 14. The assembly 55 alsoincludes a communication panel 902 to which the back pressure regulatormodules 53 attach for communication to and from the computer controller18 (FIG. 3). The modules 53 plug into the housing 900 and onto thecommunication panel 902. Accordingly, if a new or substitute module 53is needed in the purification system, it can be installed quickly andeasily upon unplugging one module and plugging in the replacementmodule.

As best seen in FIG. 10, the pressure regulator module 53 includes ahousing 1002 that contains and protects a regulator assembly 1004. Theregulator assembly 1004 controls the back pressure in the sample flow asit moves through the respective purification channel 14. The regulatorassembly 1004 is electrically connected to a stepper motor controller1006 which activates and adjusts the regulator assembly as needed duringa purification run. The stepper motor controller 1006 is connected to aprinted circuit board 1008 which also attaches to the housing 1002. Theprinted circuit board 1008 includes a plurality of connectors 1010 thatreleasably plug into the communication panel 902 (FIG. 9) of theregulator assembly. Accordingly, communication to and from the computercontroller 18 is provided to the pressure regulator module 53 throughthe printed circuit board and to the regulator assembly 1004 via thestepper motor controller 1006.

The pressure regulator module 53 also includes a front faceplate 1012that mounts to the housing 1002. The front faceplate 1012 has an inletport 1014 into which the tubing of the purification channel extends soas to allow the sample flow 31 to pass into the pressure regulatormodule 53. The sample flow passes through a pressure sensor 1013, whichis also coupled to the printed circuit board 1008, so as to identify thesample flow's pressure. After the sample flow 31 enters the regulatorassembly 1004 and the sample flow's pressure is modified as needed, asdiscussed in greater detail below, the sample flow exits the pressureregulator module 53 through an outlet port 1018 on the front faceplate1012.

As best seen in FIGS. 11 and 12, the regulator assembly 1004 includes astepper motor 1100 having wiring 1102 that connects to the stepper motorcontroller 1006 (FIG. 10). The stepper motor 1100 is connected to amotor mount 1104 that interconnects the stepper motor to a back pressureregulator 1106. The back pressure regulator 1106 is securely retained tothe stepper motor 1100 by a plurality of mounting screws 1108 thatextend through the motor mount 1104 and screw into the housing of thestepper motor 1100.

The regulator assembly 1004 also includes a heater 1110 adapted to heatthe sample flow 31 within the purification channel's tubing so as toprevent formation of ice crystals or the like that may occur as a resultof pressure differentials occurring across the pressure regulator. Theheater 1110 includes a heat transfer body 1112 that extends over theback pressure regulator 106 and a heater band 1114 clamped onto the heattransfer body by a band clamp 1116. The heater band 1114 is coupled tothe computer controller 18 to allow the heater band to regulate itstemperature to provide different heating configurations to the backpressure regulator during a purification run. The heat transfer body1112 includes a temperature sensor 1118 that monitors the temperature ofthe heat transfer body during the purification run. The temperaturesensor 1118 is coupled to the computer controller 18 (FIG. 3) so thecomputer controller can regulate the heat provided from the heater band1114 as needed during operation of the regulator assembly 1004.

As best seen in FIG. 12, the regulator 1106 has an inlet port 1200 thatreceives the purification tube 1201 carrying the sample flow 31. Theinlet port 1200 has an inlet channel 1202 that communicates with anozzle 1204 positioned below the inlet port. The nozzle 1204 in theillustrated embodiment is a ceramic component having a diamond coatingso as to provide an extremely hard and durable nozzle within theregulator. The nozzle 1204 is exposed to very harsh conditions,including caustic solvents and pressures of approximately 2000 psi orgreater. The inlet port 1200 is threadably connected to the nozzleretainer 1205 so the inlet port is easily removable to provide access tothe nozzle 1204 if replacement of a nozzle is necessary.

The nozzle 1204 includes an inlet channel 1211 extending therethroughthat communicates with a very small chamber that receives the sampleflow 31 from the nozzle's inlet channel. The lower end of the inletchannel 1211 forms a nozzle orifice through which the sample flowpasses. A stem 1208 positioned below the nozzle 1204 extends through aseal 1210, into the small chamber 1206, and terminates immediatelyadjacent to the nozzle orifice at the lower end of the inlet channel1211. The stem 1208 is moveable relative to the nozzle orifice so as toadjustably close the flow path through the regulator 1206. In theillustrated embodiment, the stem 1208 is a sapphire stem. In alternateembodiments, the stem 1208 can be made of other very hard materials,such as diamond, ruby or the like. The stem 1208 is movable relative tothe nozzle 1204 to adjust the opening size so as to regulate thepressure of the sample flow 31.

The sample flow 31 moves from the nozzle 1204 through the orifice andinto an outlet channel 1212 that is in fluid communication with thesmall chamber 1206. The outlet channel 1212 extends through an outletport 1214 that receives the exit tube 1201 therein so as to carry thesample flow 31 out of the regulator 1106. The exit tube 1201 extendsfrom the outlet port 1214 and wraps around the heat transfer body 1112approximately two times so the exit tube is heated, thereby preventingthe formation of ice crystals within the purification tube andcondensation on the outside of the exit tube. The purification tube 1201then extends from the heat transfer body 1112 away from the regulatorassembly and to the outlet port 1018 on the regulator module's faceplate1012 (FIG. 10) as discussed above.

In the illustrated embodiment, the stem 1208 is a sapphire stem havinghardness characteristics suitable for use in the high pressure and harshenvironment within the regulator assembly 1004. The sapphire stem 1208is connected at its lower end to a rod 1218 movably positioned within aholding member 1220 having a threaded lower end. The holding member 1220contains a biasing member 1222, such as Bellville washers, wave washers,or the like, that bias the rod 1218 and the stem 1208 toward the nozzle1204. In the event the stem 1208 directly engages the nozzle 1204 or issubjected to an extremely high pressure pulse, the biasing member 1222will compress so as to avoid damaging the sapphire stem 1208 or thenozzle 1204 during operation. The biasing member 1222, however, has asufficient spring stiffness so it is not compressed during normalpressures of the sample flow within the tubing of the purificationchannel 14 during a purification run.

Adjustment of the regulator assembly 1106 is provided by dual concentricscrews that move the stem 1208 relative to the nozzle 1204. As best seenin FIG. 12, the holding member 1220 is threaded into internal threads1230 formed in a shaft 1224 of an adjustment screw 1226. In theillustrated embodiment, the internal threads 1230 have a pitch of 28threads per inch (tpi). The adjustment screw's shaft 1224 also hasexternal threads 1232 that screw into a threaded aperture in theregulator body 1106. In the illustrated embodiment, the external threads1232 have a pitch of 27 tpi. Accordingly, the external threads 1232 ofthe adjustment screw 1226 have a thread pitch different than the pitchvalue of the internal threads 1230. The internal and external threads1230 and 1232 are both right-handed pitch threads oriented in opposingdirections so as to form the dual concentric adjustment screwconfiguration for attenuated movement of the stem 1208 relative to thenozzle 1204 for each turn of the adjustment screw.

The adjustment screw 1226 has an internal driving spline 1234 thatsecurely engages a drive spline 1236 on the stepper motor 1100. Thedrive spline 1236 is press fit into the internal driving spline 1234.When the stepper motor 1100 is activated by the computer controller 18(not shown), the driving spline 1236 rotates, thereby rotating theadjustment screw 1226. As the adjustment screw 1226 rotates onerevolution, the dual concentric screw configuration counteracts therange of motion of the holding member 1228, and thus the stem 1208. Asan example, if the stepper motor 1100 rotates the adjustment screw onefull revolution, the holding member 1220 moves only one pitch valuebecause of the pitch differentiation between the internal and externalthreads 1230 and 1232.

In one embodiment, one revolution of the adjustment screw along theexternal threads 1232 would move the adjustment screw 1226 and theholding member 1220 approximately 0.0373 inches. The internal threads1230, however, move in the opposite direction approximately 0.03571inches, resulting in a net movement of approximately 0.0013 inches.Accordingly, the dual concentric screw configuration within theregulator 1106 provides for extremely accurate and fine adjustments ofthe stem 1208 relative to the nozzle 1204 to closely control pressureregulation within the sample flow 31 as it passes through the backpressure regulator assembly 1004.

The back pressure regulator 1004 is formed with a minimum amount of deadvolume and unswept volume within the purification channel extendingtherethrough to prevent or minimize the risk of cross contaminationbetween purification runs for different samples. The back pressureregulator assembly is constructed with extremely durable components thatwill withstand the harsh environments experienced during thepurification run at very high pressures, while providing sufficientsafety characteristics to avoid damaging the back pressure regulator inthe event of pressure spikes or the like.

In one embodiment, the stepper motor includes a rotational stop 1238that prevents travel of the drive spline 1236 and, thus, the adjustmentscrew 1226 past a selected position relative to the regulator. Thetravel stop 1238 is positioned to block the stepper motor from drivingthe sapphire stem 1208 too far relative to the nozzle 1204, therebypreventing damage from overdriving from the stepper motor and crushingthe sapphire stem against the nozzle.

The illustrated embodiment of the purification system utilizes theregulator assembly with the dual concentric screw configurationcontrolled by the computer controller 18. In alternate embodiments, thepressure regulator assembly 53 can be a stand alone regulator withselected control mechanisms.

As best seen in FIG. 3, the sample flow 31 travels from the pressureregulator assembly 55 to the microsample valve 38. The microsample valve38 is operatively connected to the computer controller 18 and isactivated by the computer controller when a peak in the sample flow 31is moving past the microsample valve. Upon activation, the microsamplevalve 38 diverts a sampling from the sample flow 31 and directs it tothe mass spectrometer 16 for analysis. The remaining portion of thesample flow 31 continues along the flow path of the respective channel14 substantially uninterrupted. Each microsample valve 38 is activatedso the sampling contains a selected portion of just the peak. The massspectrometer 16 analyzes the sampling and determines whether the peak isa target compound or not.

As the four sample flows 31 moves simultaneously through the respectivechannels 14 and through the detectors 34, the peaks from the fourchannels will likely occur at separate times during the sample runs.Accordingly, the mass spectrometer 16 usually receives the samplingsfrom the four channels with some time between the samplings. In somecases, however, two or more detectors 34 may detect a peak in its sampleflow at the same time or at overlapping times during the sample run. Thecomputer controller 18 is programmed with an analysis priority protocolthat controls the activation sequence of the microsample valve 38 whenpeaks in the different channels 14 occur at the same time or overlappingtimes. Accordingly, the priority protocol controls the timing of whenthe samplings of the peaks are diverted to the mass spectrometer 16, soeach peak can be analyzed separately by the same analyzer. In oneembodiment, when a peak from separate channels 14 are detectedsimultaneously, the computer controller 18 activates the microsamplevalves 38 at different times so samplings of the respective peaks aresequentially directed to the mass spectrometer 16. Activation of eachmicrosample valve 38 can be controlled by revising the computercontroller's analysis priority protocol to provide sequential sampling.

As best seen in FIG. 13, the four microsample valves 38 are part of amicrosample valve assembly 1300 that has four valve modules 1302. Eachvalve module 1302 contains a microsample valve 38 for its respectivepurification channel 14. The valve modules 1302 are removably receivedby a housing 1304 and plug into connectors coupled to a communicationpanel 1306. The communication panel 1306 is, in turn, coupled to thecomputer controller 18 (not shown), so the computer controller cancontrol the activation of each microsample valve 38.

As best seen in FIGS. 14A and 14B, each valve module 1302 includes afaceplate 1400 and opposing side plates 1402 that securely engage themicrosample valve 38. The faceplate 1400 has an inlet port 1404 and anoutlet port 1406 that receive the purification channel's tubing anddirect the sample flow into and out of the valve module 38.

The microsample valve 38 includes a valve body 1408 positioned between apair of electromagnetic solenoids 1410. The solenoids 1410 areactivatable by the computer controller 18 (not shown) to controlactivation of the microsample valve, as discussed in detail below. Thesolenoids 1410 are each sandwiched between the valve body 1408 and outermounting plates 1414, and mounting screws 1416 secure the outer mountingplates to the valve body.

As best seen in FIGS. 15-17, the valve body 1408 has a sample inlet port1502, a sample outlet port 1504 (FIG. 15), a solvent inlet port 1506,and a flow outlet port 1508. The solvent inlet port 1506 is axiallymisaligned with the flow outlet port 1508. The flow outlet port 1508 isin fluid communication with the mass spectrometer 16, so fluid exitingthe microsample valve 38 through the flow outlet port is carried to themass spectrometer 16 (FIG. 3). The microsample valve 38 has a stem 1510slidably disposed within an interior chamber 1512 in the valve body1408. The stem 1510 slidably extends through the valve body 1408 and isconnected at opposite ends to the electromagnetic solenoids 1410. Thesolenoids 1410 control the stem's axial position within the valve body1408. The solenoids 1410 are connected to the computer controller 18(FIG. 3), so the computer controller can control or adjust the stem'saxial position. Upper and lower seals 1514 are positioned within thevalve body 1408 adjacent to the solenoids 1410, and a center plasticsleeve 1516 extends between the upper and lower seals. The stem 1510extends through the upper and lower seals 1514 and the plastic sleeve1516 such that a fluid-tight seal is formed therebetween. In theillustrated embodiment, the stem 1510 is press fit into the plasticsleeve 1516, thereby preventing dead space around the stem.

As best seen in FIGS. 16 and 17, the stem 1510 has a through hole 1518in fluid communication with the flow outlet port 1508 and to the massspectrometer 16. The stem 1510 also has an axial groove 1520 on theoutflow side of the valve body 1408 and in fluid communication with theflow outlet port 1508. The axial groove 1520 extends upwardly from thethrough hole 1518, along the stem's surface, and is sized to direct thefluid flow upwardly from the through hole along the groove between thestem's surface and the center plastic sleeve 1516. The through hole 1518is shaped and sized to allow either a flow of carrier solvent or asampling of a peak from the sample flow to pass toward the massspectrometer 16.

Referring now between FIGS. 3, 15 and 16, the solvent inlet port 1506(FIGS. 15 and 16) is connected to a carrier solvent line 1602 thatconnects to a carrier solvent source 1604 (FIG. 3) and a carrier solventpump 1606. The carrier solvent pump 1606 is also coupled to the computercontroller 18 that controls the flow of carrier solvent to themicrosample valves 38. A substantially continuous flow of carriersolvent is provided to the microsample valves 38 during a purificationrun. In the illustrated embodiment, the carrier solvent line 1602connects to all four microsample valves 38 in series, so the carriersolvent will flow through all of the microsample valves and to the massspectrometer. Accordingly, the carrier solvent enters the firstmicrosample valve 38 through the solvent inlet port 1506 (FIGS. 15 and16), exits through the flow outlet port 1508 (FIG. 16), back into thecarrier solvent line 1602, and into the next microsample valve throughits solvent inlet port. The flow continues through each microsamplevalve 38 and then to the mass spectrometer 16.

The microsample valve 38 in each purification channel 14 also has acontinuous flow of the sample flow 31 passing through it. The sampleflow 31 enters the microsample valve 38 through the sample inlet port1502 (FIGS. 15 and 16), through a sample line 1522 extending through thevalve body 1408 immediately adjacent to the stem 1510, and out throughthe sample outlet port 1504. Accordingly, the sample flow 31 in theillustrated embodiment is transverse to the flow of the carrier solvent.

When the microsample valve 38 is in a lowered normal position, shown inFIG. 16, the through hole 1518 is below and out of communication withthe sample flow 31. The stem 1510 blocks the sample flow 31 from passingthrough the flow outlet port 1508 to the mass spectrometer 16 (FIG. 3).When the stem 1510 is in the lowered position, a continuous flow ofcarrier solvent passes into the valve body 1408 through the solventinlet port 1506, through the through hole 1518, up the axial groove1520, and out of the valve body 1408 through the flow outlet port 1508toward the mass spectrometer 16.

During normal use, when a peak has not been identified, the microsamplevalve 38 remains in this lowered normal position, so only the carriersolvent flows through the microsample valves to the mass spectrometer16. When the detector 34 (FIG. 3) detects a peak in the sample flow 31and the computer controller 18 activates the microsample valve 38, thesolenoids 1410 immediately move the stem 1510 axially from the loweredposition to a raised sampling position, shown in FIG. 17. In this raisedsampling position, the through hole 1518 in the stem 1510 is in fluidcommunication with the sample line 1522 through which the sample flow 31travels between the sample inlet and outlet ports 1502 and 1504.Accordingly, the flow of carrier solvent is temporarily interrupted anda small sampling of the peak traveling through the sample line 1522 isdiverted from the sample line, through the through hole 1518 to the flowoutlet port 1508, and into the carrier line at the location where thecarrier solvent flow was interrupted. The sampling then flows to themass spectrometer 16 (FIG. 3) for analysis.

As the peak is moving past the through hole 1518 at a selected time, asdetermined by the computer controller 18, the stem 1510 is switched backto the lowered position (FIG. 16). The solenoids 1410 are activated,thereby immediately moving the stem 1510 axially to the loweredposition, so the only part of the sample flow 31 received by the massspectrometer 16 for analysis is the sampling of the peak. When the stem1510 is returned to the lowered position, the flow of the carriersolvent to the mass spectrometer 16 is resumed. Therefore, the massspectrometer 16 receives a continuous flow of fluid, and the samplingsare effectively inserted as segments of that continuous flow when themicrosample valve 38 is activated.

The axial movement of the stem 1510 between the lowered position and theraised sampling position allows for an extremely fast switching betweenpositions, thereby providing for small yet highly accurate samplings ofthe selected portion of the sample flow. In the illustrated embodiment,the microsample valve 28 is configured to be switched from the normallowered position, to the raised sampling position and back to the normallowered position within a time period of approximately 15 to 100milliseconds. In one embodiment the time period is less than 20milliseconds, so as to divert sample volumes as small as approximately 2pico liters or less to the mass spectrometer 16. In an alternateembodiment, the microsample valve 28 is configured to be movable fromthe normal lowered position, to the raised sampling position and back tothe normal lowered position in one second or less. This extremely fastswitching also minimizes the chance of cross-contamination within thevalve body between samplings of a plurality of peaks within the sampleflow.

The microsample valve 38 is designed and constructed so the flow pathsthrough the valve body 1408 and the stem 1510 provide virtually no deadspace or unswept volumes that could cause cross-contamination betweendifferent samples flowing through the microsample valve. Accordingly,the microsample valve 38 allows for very accurate results in thepurification process. The microsample valve 38 is also configured toquickly take the small sample portions from the sample flow, therebyminimizing the pressure drop in the sample flow across the microsamplevalve 38. In the illustrated embodiment, the pressure drop across themicrosample valve is less than approximately 50 psi.

As best illustrated in FIG. 3, the sample flow 31 in each channel 14moves from the microsample valve 38 to a pressure relief valve assembly41 that controls the pressure within the flow downstream of themicrosample valve. In the illustrated embodiment, the pressure reliefvalve assembly 41 has the same construction as the back pressureregulator assembly 55 discussed above, except that the heaters are notprovided on the back pressure regulator valve. In alternate embodiments,the heaters can be used if needed as a result of ice formation or largerpressure drops experienced in the system. In other alternateembodiments, other back pressure regulators can be used, provided theyare durable enough and provide sufficient pressure control for thepurification valve.

The use of the pressure relief valve 41 allows the flow volume to theanalyzer to be very small because of either use of a small borecapillary to the analyzer or an active back-pressure regulator.Accordingly, the pressure differential is reduced and the flow volume tothe mass spectrometer 16 is reduced.

The sample flow 31 exits the pressure relief valve assembly 41 and flowsto a flow directing valve, referred to as a fraction collection valve40. Each fraction collection valve 40 has one inlet port 42, two outletports 44 and 46, and a waste port 47. Each fraction collection valve 40is also operatively coupled to the computer controller 18. When aportion of the sample flow 31 containing a peak enters the fractioncollection valve 40 through the inlet port 42, as identified by thecomputer controller 18, the computer controller activates the fractioncollection valve to control whether the peak in the sample flow isdirected out of the first outlet port 44 or the second outlet port 46.

If the mass spectrometer 16 determines that the peak is the targetcompound, the computer controller 18 activates the fraction collectionvalve 40, so the fraction collection valve moves to a first position. Inthis position, the sample portion containing the peak is directed out ofthe fraction collection valve 40 through the first outlet valve 44. Thesample portion is directed to a fraction collector assembly 43 and iscollected directly into a predetermined location in a selected well ofthe first receiving microtiter plate 22.

When a portion of a sample flow containing a peak passes through thefraction collection valve 40, and that peak is a crude rather than thetarget compound, the fraction collection valve is switched to a secondposition to direct a portion of the sample flow through the secondoutlet port 46. This portion of the sample flow 31 exits the secondoutlet port 46, passes through the fraction collection assembly 43 andis collected directly into a selected well of the second receivingmicrotiter plate 24. When a portion of the sample flow 31 passes throughthe fraction collection valve and that portion does not contain anypeaks, the sample flow passes through the waste outlet 47 and is carriedto a waste receptacle 52.

The purification system 10 of the exemplary embodiment allows thepurified samples to be automatically dispensed into selected wells ofthe receiving microtiter plate 22 or 24, where each sample is dispensedinto a well having the same relative location in the receivingmicrotiter plate as the supply microtiter plate well from which thesample was initially drawn to begin the purification run. Therefore, thepurified target compound is deposited directly into a well having aone-to-one corresponding well address as the original sample well.Similarly, the crudes are deposited directly into a well having acorresponding well address and the second receiving microtiter plate, sothe crudes are collected separately from the purified target compounds.This direct depositing of the target compounds into a selectedmicrotiter plate well avoids further processing and formatting beforethe purified target compounds are put into microtiter plates.Accordingly, the efficiency of the purification process is increased andthe time and cost requirements are decreased.

This purification system 10 of the illustrated embodiment results in thecollection of purified compounds having an 85% purity or better. It ispreferred, of course, to provide samples having purity as close to 100%pure as possible. Upon collection of the purified target compounds inthe receiving microtiter plate 22, these purified target compounds areready for a screening process or other selected process.

As best seen in FIG. 20, the fraction collector assembly 43 includes aframe 2000 that supports a docking station 2002 that removably receivesthe receiving microtiter plates 22 and 24. The fraction collectorassembly 43 also includes a dispensing head 2004 that travels laterallyalong a rail 2006 mounted to the frame 2000 between several operatingpositions, discussed below.

The fraction collector assembly 43 includes a hopper 2008 that containsclean, disposable expansion chambers 2010. The fraction collectorassembly 43 is configured to provide the expansion chambers 2010 fromthe hopper 2008 to a pickup station 2012. The pickup stations 2012 holdsthe expansion chambers 2010 in a substantially vertical orientation withan open top end 2020 of the expansion chamber facing upwardly. Thedispensing head 2004 is movable to a position over the pickup station2012 and movable downwardly so dispensing needles 2014 on the dispensinghead 2004 extend into the expansion chambers. The dispensing head 2004then grasps the expansion chambers 2010 and lifts them from the pickupstation 2012.

As best seen in FIG. 21, the dispensing head 2004 moves the expansionchambers 2010 from the pickup station 2012 to a dispensing position overselected wells 2024 in the microtiter plates 22 and 24. The dispensinghead 2004 is coupled to the computer controller 18 that controls thepositioning of the expansion chambers 2010 over the wells 2024 so as tocorrespond to the well locations from which the sample was originallytaken. The dispensing head 2004 moves the expansion chambers 2010downwardly so as to extend at least partially into the selected wells2024. Once the expansion chamber 2010 is lowered, the sample portioncontaining either the target or the crude is deposited from thedispensing needle 2014, into the expansion chamber 2010, and into theselected well 2024 in the microtiter plate 22 or 24.

As best seen in FIG. 18, the dispensing head 2004 of the illustratedembodiment releasably holds two expansion chambers 2010 in tubularholding members 2011. A pneumatic gripping assembly 2015 is connected toeach tubular holding member 2011 in a position to releasably engage theexpansion chambers 2010. The gripping assembly 2015 includes a pair ofgrippers 2017 connected to pneumatic cylinders 2019. The pneumaticcylinders 2019 move the grippers 2017 relative to the tubular holdingmember 2011 between holding and released positions. In the holdingposition, each gripper 2017 presses the expansion chamber 2010 againstthe tubular holding member 2011, so the expansion chamber isfrictionally held in the tubular holding member. In the releasedposition, each gripper 2017 is positioned to allow the respectiveexpansion chamber 2010 to freely move into or out of the tubular holdingmember 2011.

The expansion chamber 2010 is a tubular member having the open top end2020 that is releasably engaged by the gripping assembly 2015 of thedispensing head 2004, and a tapered, open bottom end 2022. The openbottom end 2022 is positionable partially within a selected well 2024 ofthe microtiter plate 22 or 24. The expansion chamber's open top end 2020is positioned so the dispensing needle 2014 extends therethrough intothe expansion chamber's interior area 2028. The dispensing needle 2014is positioned adjacent to the expansion chamber's sidewall so the needleis not coaxially aligned with the expansion chamber. The distal end 2013of the dispensing needle 2014 is angled so as to point toward therespective expansion chamber's sidewall.

As the sample portion is dispensed from the dispensing needle 2014 intothe interior area 2028 of the expansion chamber 2010, the sample portionis in an atomized state. The atomized sample portion enters theexpansion chamber 2010 through the needle's angled distal end 2013, andthe distal end direct the flow toward the expansion chamber's sidewall.The atomized sample portion condenses on the expansion chamber'ssidewalls as a liquid, and is directed so the condensed liquid movesalong the sidewalls in a downwardly spiral direction.

The condensed, non-atomized liquid sample portion flows out of the openexpansion chamber's bottom end 2022 into the selected well 2024 in themicrotiter plate 22 or 24. As the atomized sample portion is beingdispensed into the expansion chamber 2010, the CO₂ vapor exits theexpansion chamber through its open top end 2020. In the illustratedembodiment, a vacuum is drawn within the expansion chamber to draw theCO₂ vapors out and away from the expansion chamber's open top end 2020,thereby avoiding cross-contamination between channels.

As the sample portion is condensed in the expansion chamber 2010, someof the liquid sample portion may remain in the bottom of the expansionchamber because of a capillary action at the narrow open bottom end2022. At this point, the fraction collection valve dispenses a selectedsolvent into the expansion chamber to rinse it out and carry anyremaining sample into the microtiter plate 22 or 24. After the sampleportion has been fully dispensed, the dispensing head 2004 can provide apuff of low pressure air into the expansion chamber 2010. The air forcesthe remaining liquid sample out of the expansion chamber 2010 and intothe well 2024.

As best seen in FIG. 21, after the sample has been dispensed into themicrotiter plate 22 or 24, the dispensing head 2004 moves to a chamberdrop-off position so the expansion chambers 2010 are positioned past theedge of the frame 2000. The gripping assembly 2015 of the dispensinghead 2004 moves to the released position and the expansion chambers 2010drop into a suitable waste receptacle. In one embodiment, the expansionchambers 2010 are thrown away. In an alternate embodiment, the expansionchambers 2010 are recycled so as to be reusable.

After the dispensing head 2004 drops off the expansion chambers, thedispensing head moves to a needle rinse position, illustrated in FIG.22. In this needle rinse position, the dispensing head 2004 ispositioned over a pair of wash stations 2030. As seen in FIGS. 19-21,the wash stations 2030 each include a wash tube 2031 that dispenses acleaning solvent or other solution. The wash tubes 2031 are sized andpositioned so the dispensing head 2004 can lower the dispensing needles2014 into the wash tube 2031. The wash station 1230 is then energizedand dispenses cleaning fluid onto the outside of the dispensing needles2014. The dispensing head 2004 is then raised washing the dispensingneedles 2014 from the top to the bottom as they are withdrawn from thewash tube 2031. The dispensing head 2004 is then moved back to theexpansion chamber pickup position, illustrated in FIG. 20, wherein newexpansion chambers are picked up and ready for dispensing other sampleportions into the microtiter plates 22 and 24.

The high throughput purification system 10 of the illustrativeembodiment allows for relatively fast sample purification as compared toconventional purification processes. A purification run of a selectedsample can be accomplished in approximately 6-8 minutes or faster.Therefore, purification of samples contained in a 96 well microtiterplate will take approximately 144-192 minutes. Purification of 4,000samples generated in a week using sample generation techniques,discussed above, will only take in the range of 250-330.3 hours, asopposed to the 2,000 hours required to purify the 4,000 samples, usingconventional purification techniques. Therefore, the high throughputpurification system in accordance with the present invention allows fora significant increased speed of purification. This system also providesfor collecting the purified samples directly into a microtiter plate inwells having a location address corresponding to the location address ofthe well in the microtiter plate from which the samples were originallydrawn. Thus, the purified compounds are ready to be screened orotherwise processed. The result is a significantly increased capacityfor purification that allows for a less expensive purification process.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

What is claimed is:
 1. A multiple channel, high throughput supercriticalfluid chromatographic purification system for substantiallysimultaneously purifying multiple samples from a chemical library, eachof the samples being separable into first and second componentscomprising: a sample analyzer that analyzes selected samplecharacteristics; a first purification channel coupled to the sampleanalyzer, the first purification channel including; a firstchromatographic sample separation device positioned to separate a firstsample flow into first and second sample components; a first detectorpositioned to detect the first and second components in the first sampleflow; a first flow diverting device moveable to direct a sampling of thefirst sample component to the analyzer and the remainder of the firstsample portion flows along a first flow path away from the divertingfirst flow device; a first collector positioned to receive at least aportion of the first or second sample component of the first sample thesample analyzer identified as having selected sample characteristics; asecond collector positioned to receive remaining components of the firstsample not having the selected sample characteristics; and a secondpurification channel coupled to the sample analyzer, the secondpurification channel including: a second chromatographic separationdevice positioned to receive a second sample flow for separation intothe first and second components of the second sample flow; a seconddetector positioned to detect the first and second components of thesecond sample flow; a second flow diverting device moveable to direct asampling of the first or second components to the analyzer and aremainder of the second sample portion flows along a second flow pathaway from the flow diverting device; a third collector positioned toreceive at least a portion of the first or second sample components ofthe second sample having the selected sample characteristics; and afourth collector positioned to receive remaining components of thesecond sample not having the selected sample characteristics.
 2. Thesystem of claim 1, further comprising a third purification channelcoupled to the sample analyzer, the third purification channelincluding: a third chromatographic separation device positioned toreceive a third sample flow for separation into the first and secondcomponents of the third sample flow; a third detector positioned todetect the first and second component portions of the third sample flow;a third flow diverting device movable to direct a sampling of the firstor second components of the third sample flow to the analyzer and aremainder the third sample portion flows along a third flow path awayfrom the third flow diverting device; the first collector beingpositioned to receive the first or second components of the third sampleflow having the selected sample characteristics; the second collectorbeing positioned to receive the remaining components of the third sampleflow not having the selected sample characteristics; and a fourthpurification channel coupled to the common sample analyzer, the fourthpurification channel including: a fourth chromatographic separationdevice positioned to receive a fourth sample flow for separation intothe first and second components of the fourth sample flow; a fourthdetector positioned to receive the first and second component of thefourth sample; a fourth flow diverting device movable to direct asampling of the first or second components of the fourth sample flow tothe analyzer and a remainder of the fourth sample portion flows along afourth flow path away from the flow diverting device; the firstcollector being positioned to receive the first or second components ofthe fourth sample having the selected sample characteristics; and thesecond collector positioned to receive the remaining components of thefourth sample not having the sample characteristics.
 3. The purificationsystem of claim 1 wherein the sample analyzer is a mass spectrometer. 4.The purification system of claim 1 wherein at least one of the fourseparation devices is a chromatography column.
 5. The purificationsystem of claim 1 wherein at least one of the four detectors is a UVdetector.
 6. The purification system of claim 1 wherein at least one ofthe first and second flow diverting devices is a microsample valve influid communication with the analyzer and movable between open andclosed positions to allow the sampling of the respective sample flows topass to the analyzer.
 7. The purification system of claim 1 wherein thesample is vaporous as it moves through the first purification channel,and further comprising an expansion chamber positioned to receive andcondense the vaporous sample to a liquid before the sample is receivedby the first or second collectors.
 8. The purification system of claim1, further comprising a pressure regulator positioned to receive thefirst sample flow and adjust a pressure of the first sample flow in thefirst purification channel upstream of the first flow diverting device.9. The purification system of claim 8 wherein the pressure regulator hasa heater portion that heats at least a portion of the first sample flow.10. The purification system of claim 1 further comprises a pressurerelief valve position downstream of the first flow diverting device. 11.The purification system of claim 1 wherein each sample is vaporous as itmoves through its respective purification channel, and furthercomprising an expansion chamber positionable to receive and condense thevaporous respective sample to a liquid before the respective sample isreceived by the first or second collectors.
 12. The purification systemof claim 1, further comprising a sample holder having a plurality ofsample receptacles including a sample receptacle, each sample receptaclebeing in a predetermined location relative to the other samplereceptacles, and the collector has a plurality of collection wells, eachcollection well having a predetermined location relative to the othercollection well, and the predetermined location of each samplereceptacle corresponds to the predetermined location of a respective oneof the collection wells.
 13. A multiple channel, high throughputpurification system for substantially simultaneously purifying at leasttwo samples from a chemical library, comprising: a controller; a sampleanalyzer coupled to the controller, the analyzer being configured todetermine whether the first sample has selected sample characteristics;at least two purification channels coupled to the common sampleanalyzer, each purification channel including: a separation devicepositioned to receive a sample flow containing the sample and toseparate the sample into first and second sample components spaced apartfrom each other in the first sample flow; a detector coupled to theseparation device, the detector being positioned to receive the sampleflow from the separation device, the detector configured to detect atleast the sample component within the first sample flow; a flow samplingdevice positioned to receive the sample flow from the detector, the flowsampling device being moveable between open and closed positions, in theopen position the flow sampling device directs a sampling of the samplecomponent to the analyzer and a remainder of the first sample flowsalong a flow path past the flow splitting device, and in the closedposition the device blocks the sample flow from passing to the analyzer;a flow directing valve in fluid communication with the flow path andpositioned to receive the sample, the flow directing valve being movableto a first position to direct the sample portion in a first direction ifthe analyzer has determined that the sample component has the selectedsample characteristics, and the flow directing valve being movable to asecond position to direct the sample portion in a second direction ifthe analyzer has determined that the sample component does not have thefirst selected sample characteristics; a first collector positioned toreceive the sample components that have the selected samplecharacteristics from the flow directing devices when the flow directingdevices are in the first position; and a second collector and positionedto receive the sample components that do not have the selected samplecharacteristics when the first flow directing devices are in the secondposition.
 14. The purification system of claim 13 wherein the commonsample analyzer is a mass spectrometer.
 15. The purification system ofclaim 13 wherein at least one of the two separation devices is achromatography column.
 16. The purification system of claim 13 whereinat least one of the two separation devices is a supercritical fluidchromatography column.
 17. The purification system of claim 13 whereinat least one of the two detectors is a UV detector.
 18. The purificationsystem of claim 13 wherein at least one of the two flow sampling devicesis a microsample valve.
 19. The purification system of claim 13 whereinthe sample flow is vaporous as it moves through the purificationchannel, and further comprising an expansion chamber positioned toreceive the vaporous sample flow and condense the selected componentflow to a liquid before it is received by the first or second collector.20. The purification system of claim 19 wherein the expansion chamber issized to receive the vaporous sample component herein and to condensethe vaporous first sample component along side walls of the expansionchamber.
 21. The purification system of claim 13 wherein the secondsample flow is vaporous as it moves through the second purificationchannel, and further comprising an expansion chamber positioned toreceive the vaporous second sample flow and to condense the secondsample to a liquid before the second sample is received by the third orfourth collector.
 22. The purification system of claim 13, furthercomprising a sample holder for each channel having a plurality of samplereceptacles including a first sample receptacle, each sample receptaclebeing in a predetermined location relative to the other samplereceptacles, and the first collector is in a collection assembly havinga plurality of collectors therein, each collector having a predeterminedlocation relative to the other collectors, and the predeterminedlocation of the first sample receptacle in the sample holder correspondsto the predetermined location of the first collector.
 23. Thepurification system of claim 13, further comprising a controlleroperatively connected to the sample analyzer, four flow splitting valvesand the four flow directing valves to control the sample flows inresponse to analysis results from the analyzer regarding the componentsfrom each of the channels.
 24. A multiple channel, high throughputpurification system for substantially simultaneously purifying at leasttwo samples from a chemical library, comprising: a sample analyzerconfigured to determine whether a sample portion passing therethroughhas selected sample characteristics; at least two purification channelscoupled to the common sample analyzer and configured to simultaneouslycarry a respective sample flow, each purification channel including: asample separation device configured to separate a selected sample intofirst and second sample components spaced apart from each other in therespective sample flow; a detector coupled to the sample separationdevice, the detector being configured to detect at least one samplecomponent within the respective sample flow; a flow sampling devicepositioned to receive the respective sample flow from the detector, theflow sampling device being moveable to direct a sampling of the samplecomponent to the analyzer and a remainder of the respective sample flowcontinues along the respective flow path; a first collector positionedto receive the sample components that have the selected samplecharacteristics from the flow directing devices when the flow directingdevices are in the first position; and a second collector and positionedto receive the sample components that do not have the selected samplecharacteristics when the first flow directing devices are in the secondposition.
 25. The system of claim 24 wherein each purification channelincludes a flow directing valve in fluid communication with therespective flow path and positioned to receive the sample portion in therespective sample flow, the flow directing valve being movable to afirst position to direct the sample portion in a first direction if theanalyzer has determined that the sample component has the selectedsample characteristics, and the flow directing valve being movable to asecond position to direct the sample portion in a second direction ifthe analyzer has determined that the sample component does not have thefirst selected sample characteristics.
 26. The system of claim 25wherein the flow directing valve is positioned to direct the sampleportion to the first collector when the flow directing valve is in thefirst position and to direct the sample portion to the second collectorwhen the flow directing valve is in the second position.
 27. The systemof claim 24 wherein the system includes four purification channels. 28.The system of claim 24, further comprising a controller coupled to theanalyzer.
 29. The system of claim 24 wherein the separation device ineach purification channel is positioned to receive the respective sampleflow before the sample flow reaches the detector and the flow samplingdevice.